Rod attachment for head to head cross connector

ABSTRACT

Exemplary spinal fixation devices, systems, and method are provided for stabilizing vertebrae in a patient&#39;s spine. In one exemplary embodiment, methods and devices are provided for coupling one or more bone anchors, such as hooks, screws, etc., and/or one or more spinal fixation elements, such as spinal rods, cables, plates, etc. In certain exemplary embodiments, a cross connector is provided for connecting and stabilizing two bone anchors, a bone anchor and a spinal fixation element, or a bone anchor and bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 13/470,597, (now U.S. Pat. No. ______) filed on May 14, 2012, which is a continuation of U.S. patent application Ser. No. 12/752,729, (now U.S. Pat. No. 8,192,471) filed on Apr. 1, 2010, which is a continuation of U.S. patent application Ser. No. 11/162,934 (now U.S. Pat. No. 7,717,939), filed on Sep. 28, 2005, both of which are entitled “Rod Attachment for Head to Head Cross Connector.” U.S. patent application Ser. No. 11/162,934 is a continuation-in-part of U.S. patent application Ser. No. 10/813,904 (now U.S. Pat. No. 7,645,294), filed on Mar. 31, 2004 and entitled “Head-To-Head Connector Spinal Fixation System.” All of the above-referenced U.S. Patent Applications are hereby incorporated by reference in their entireties.

BACKGROUND

Spinal fixation devices are used in orthopedic surgery to align and/or fix a desired relationship between adjacent vertebral bodies. Such devices typically include a spinal fixation element, such as a relatively rigid fixation rod, that is coupled to adjacent vertebrae by attaching the element to various anchoring devices, such as hooks, bolts, wires, or screws. Alternatively, two rods can be disposed on the lateral or anterior surface of the vertebral body in a substantially parallel relationship. The fixation rods can have a predetermined contour that has been designed according to the properties of the target implantation site, and once installed, the rods hold the vertebrae in a desired spatial relationship, either until desired healing or spinal fusion has taken place, or for some longer period of time.

Spinal cross connectors are often used in conjunction with spinal fixation devices to provide additional stability to the devices. For example, it has been found that when a pair of spinal rods are fastened in parallel on either side of the spinous process, the assembly can be significantly strengthened by using a cross connector to bridge the pair of spinal rods. The connectors are typically in the form of a rod having a clamp formed on each end thereof for mating with a spinal rod.

While current spinal cross connectors have proven effective, difficulties have been encountered in mounting the cross connectors, and maintaining them in a desired position and orientation with respect to the spinal rod, or other spinal fixation device to which they are attached. In particular, the clamp assemblies often consist of several parts which make surgical application tedious, and which can also increase the manufacturing costs. Since the cross connector is often applied as the last step in a lengthy surgical procedure, ease of application is paramount. Fixation of the cross connector to spinal rods can also be difficult where the rods are not parallel to one another, or they are diverging/converging with respect to one another, or where other spinal fixation devices interfere with proper placement.

Accordingly, there exists a need for an improved spinal cross connector that can be easily installed and that securely mates to and connects spinal fixation devices.

SUMMARY

The present invention relates to spinal fixation systems and method for stabilizing vertebrae in a patient's spine. In an exemplary embodiment, methods and device are provided for coupling one or more bone anchors, such as hooks, screws, etc., and/or one or more spinal fixation elements, such as spinal rods, cables, plates, etc. In certain exemplary embodiments, a cross connector is provided for connecting and stabilizing two bone anchors, a bone anchor and a spinal fixation element, or a bone anchor and bone.

In one exemplary embodiment, a spinal fixation system is provided having a cross connector that is configured to span between opposed lateral sides of a vertebra and having first and second ends. A coupling member is configured to mate to the first end of the cross connector and it can include a rod-receiving recess formed therein for coupling to a spinal rod. The coupling member is preferably configured to couple to a spinal rod without anchoring to bone. The system can also include a bone anchor having a shaft for engaging bone and a head configured to mate to the second end of the connector and having a rod-receiving recess formed therein for coupling to a spinal rod.

The coupling member can have a variety of configurations, and in one embodiment it can have a side-loading rod-receiving recess, i.e., the coupling member is loaded onto a spinal rod from the side. For example, the rod-receiving recess formed in the coupling member can be defined by a top wall, a bottom wall, and a side wall connecting the top and bottom walls. In an exemplary embodiment, the top wall includes a thru-bore formed therein for receiving a fastening element adapted to mate the coupling member to the cross connector. The system can also include a fastening element that is adapted to extend through an opening formed in the first end of the cross connector and to extend into the thru-bore formed in the top wall of the coupling member for mating the coupling member to the cross connector. The fastening element can also extend into the rod-receiving recess to lock a spinal rod disposed therein to the coupling member.

In another embodiment, the coupling member can have a top-loading rod-receiving recess, i.e., the coupling member is loaded onto a spinal rod from the top. For example, the rod-receiving recess formed in the coupling member can be defined by a top wall and first and second side walls extending from opposed sides of the top wall. In an exemplary embodiment, the top wall includes a thru-bore formed therein for receiving a fastening element adapted to mate the coupling member to the cross connector.

In other embodiments, the coupling member can include features to facilitate locking of a spinal rod therein. For example, the coupling member can include a locking arm extending into the rod-receiving recess and adapted to extend around at least a portion of a rod disposed within the rod-receiving recess. In an exemplary embodiment, the locking arm extends through one of the first and second side walls of the coupling member. A fastening element can extend through an opening formed in the first end of the cross connector and into the thru-bore formed in the top wall of the coupling member to abut against the locking arm and thereby lock a rod within the rod-receiving recess of the cross connector.

In other embodiments, the coupling member can include at least one movable member adapted to move in response to a force applied thereto by the fastening element to engage a rod disposed within the rod-receiving recess. The movable member can be one or more pivoting or sliding wedges. For example, the coupling member can include a wedge disposed therein and adapted to be engaged by the fastening element such that the wedge moves to engage a rod disposed within the rod receiving recess of the coupling member.

Exemplary methods for spinal stabilization are also provided. In one embodiment, the method can include coupling a first end of a cross connector to a head of a bone anchor to anchor the first end of the cross connector to a first vertebra, the bone anchor having a first spinal rod extending therethrough, and coupling a second end of the cross connector to a second spinal rod without anchoring the second end of the cross connector to the first vertebra. In an exemplary embodiment, the second spinal rod is positioned within a rod receiving recess of a coupling member, and a fastening element is inserted through the second end of the cross connector and into an opening formed in the coupling member to lock the spinal rod, coupling member, and cross connector to one another. Depending on the configuration of the coupling member, the spinal rod can be side-loaded into a rod-receiving recess formed in a sidewall of the coupling member, or it can be bottom-loaded into a rod-receiving recess formed in a bottom wall of the coupling member. The fastening element can then be inserted into an opening formed in a top wall of the coupling member to lock the rod therein and to mate the coupling member to the cross connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is an exploded perspective view of one embodiment of a spinal fixation system;

FIG. 1B is a cross-sectional view of the spinal fixation system shown in FIG. 1A in an assembled configuration;

FIG. 2A is a perspective view of the connecting plate of the spinal fixation system shown in FIGS. 1A and 1B;

FIG. 2B is a top view of the connecting plate shown in FIG. 2A;

FIG. 2C is a side view of the connecting plate shown in FIG. 2A;

FIG. 3A is a perspective view of a set screw of the spinal fixation system shown in FIGS. 1A and 1B;

FIG. 3B is a side view of the set screw shown in FIG. 3A;

FIG. 3C is a top view of the set screw shown in FIG. 3A;

FIG. 4A is a perspective view of the cap of the spinal fixation system shown in FIGS. 1A and 1B;

FIG. 4B is a top view of the cap shown in FIG. 4A;

FIG. 4C is a side view of the cap shown in FIG. 4A;

FIG. 5A is a cross-sectional, partially assembled view of the first end of the spinal fixation system shown in FIGS. 1A and 1B, showing domed bearing surfaces;

FIG. 5B is a cross-sectional view of another embodiment of a partially assembled end portion of a spinal fixation system having bearing surfaces;

FIG. 6A is a cross-sectional view of an end portion of another embodiment of a spinal stabilization system;

FIG. 6B is a cross-sectional view of an end portion of yet another embodiment of a spinal stabilization system;

FIG. 7A is a perspective view of the set screw of the spinal stabilization system shown in FIG. 6B;

FIG. 7B is a side view of the set screw shown in FIG. 7A;

FIG. 7C is a top view of the set screw shown in FIG. 7A;

FIG. 7D is a cross-section view of the set screw shown in FIG. 7A;

FIG. 8A is a perspective view of yet another embodiment of a set screw;

FIG. 8B is a side view of the set screw shown in FIG. 8A;

FIG. 8C is a top view of the set screw shown in FIG. 8A;

FIG. 8D is a cross-section view of the set screw shown in FIG. 8A;

FIG. 9 is a cross-sectional view of another embodiment of a cap having a threaded post extending therefrom;

FIG. 10 is an exploded perspective view of another embodiment of a spinal fixation system that includes a floating washer;

FIG. 11A is a perspective view of the floating washer of the spinal fixation system shown in FIG. 10;

FIG. 11B is a side view of the floating washer shown in FIG. 11A;

FIG. 11C is a top view of the floating washer shown in FIG. 11A;

FIG. 12A is a perspective view of one embodiment of a connecting plate;

FIG. 12B is a top view of the connecting plate shown in FIG. 12A;

FIG. 12C is a side view of the connecting plate shown in FIG. 12A;

FIG. 13A is a perspective view of another embodiment of a connecting plate;

FIG. 13B is a top view of the connecting plate shown in FIG. 13A;

FIG. 13C is a side view of the connecting plate shown in FIG. 13A;

FIG. 14A is a perspective view of yet another embodiment of a connecting plate;

FIG. 14B is a top view of the connecting plate shown in FIG. 14A;

FIG. 14C is a side view of the connecting plate shown in FIG. 14A;

FIG. 15A is a perspective view of yet another embodiment of a spinal fixation system;

FIG. 15B is an exploded view of the spinal fixation system shown in FIG. 15A;

FIG. 16A is a perspective view of another embodiment of a connecting plate;

FIG. 16B is a top view of the connecting plate shown in FIG. 16A;

FIG. 16C is a side view of the connecting plate shown in FIG. 16A;

FIG. 17A is an illustration of the connecting plate shown in FIG. 16A mated to a vertebra in a patient's spine for supporting the spinous process in the rotated position during a partial laminoplasty;

FIG. 17B is an illustration of the connecting plate shown in FIG. 16 and a second connecting plate mated to opposed lateral sides of a vertebra in a patient's spine for supporting the spinous process during a total laminoplasty;

FIG. 18A is a cross-sectional view of another embodiment of a spinal stabilization system having a connecting plate with a first end mated to a bone anchor and a second end with a side-loading coupling member mated directly to a spinal fixation element;

FIG. 18B is an exploded view of the spinal stabilization system shown in FIG. 18A;

FIG. 18C is a side view of the side-loading coupling member of the spinal stabilization system shown in FIG. 18A;

FIG. 19A is a cross-sectional view of another embodiment of a spinal stabilization system having a connecting plate with a first end mated to a bone anchor and a second end with a top-loading coupling member mated directly to a spinal fixation element;

FIG. 19B is an exploded view of the spinal stabilization system shown in FIG. 19A;

FIG. 19C is a side view of the top-loading coupling member of the spinal stabilization system shown in FIG. 19A;

FIG. 20 is a side view of another embodiment of a top-loading coupling member having wedges disposed therein and adapted to engage a spinal fixation element;

FIG. 21A is an exploded view of another embodiment of a top-loading coupling member having an offset wedge that is adapted to engage a spinal fixation element; and

FIG. 21B is a cross-sectional, assembled view of the top-loading coupling member shown in FIG. 21A.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

In general, various spinal fixation systems are provided for aligning and/or fixing a desired relationship between adjacent vertebral bodies. In one exemplary embodiment, the spinal fixation system includes one or more bone anchors, such as bone screws, one or more spinal fixation elements, such as spinal rods, plate, or cables, and one or more connecting plates. In use, one or more bone anchors can be implanted in one or more adjacent vertebrae, for example in the pedicle, lamina, or lateral mass of a vertebra, and the spinal fixation element(s) can extend generally along the axis of the spine between one or more bone anchors. The connecting plate(s) can couple to and extend between two bone anchors, or a bone anchor and a spinal fixation element, positioned on opposed sides of the spine, thus providing additional stability to the assembly. In one embodiment, the connecting plate can protect the spinal cord after a full or partial laminectomy.

FIGS. 1A and 1B illustrate one exemplary embodiment of a spinal fixation system 100 having a connecting plate that is adapted to extend between two bone anchors. As shown, the system 100 generally includes first and second bone anchors in the form of bone screws 102 a, 102 b, first and second spinal fixation elements in the form of spinal rods 104 a, 104 b that are connected to the first and second bone anchors 102 a, 102 b, respectively, and a connecting plate 106 extending between the first and second bone anchors 102 a, 102 b. While the rods 104 a, 104 b and the connecting plate 106 can be mated to the bone anchors 102 a, 102 b using a variety of techniques, in the illustrated embodiment the spinal fixation system 100 includes first and second set screws 116 a, 116 b that threadably engage a rod receiving portion 114 a, 114 b of each bone anchor 102 a, 102 b to mate the spinal fixation rods 104 a, 104 b to the bone anchors 102 a, 102 b, and first and second caps 118 a, 118 b that threadably engage the set screws 116 a, 116 b to fix the connecting plate 106 to the rod-receiving portion 114 a, 114 b of each bone anchor 102 a, 102 b. In use, the bone anchors 102 a, 102 b can be implanted in opposed lateral sides of a vertebra, and the spinal rods 104 a, 104 b can extend through the bone anchors 102 a, 102 b to couple the bone anchors 102 a, 102 b to one or more spinal anchors implanted in adjacent vertebrae. The connecting plate 106 can be mated to the first and second bone anchors 102 a, 102 b using the set screws 116 a, 116 b and the caps 118 a, 118 b, thereby providing additional stability to the spinal stabilization system 100.

Each bone anchor 102 a, 102 b can have a variety of configurations, and various bone anchors known in the art may be used with the spinal stabilization system 100, including, for example, monoaxial bone screws, polyaxial bone screws, bolts, hooks, or any other implant or combination of implants designed to engage bone and connect to a spinal fixation element, such as a spinal rod 104 a, 104 b. In the illustrated embodiment, the bone anchors 102 a, 102 b are polyaxial bone screws, each having a distal portion 110 a, 110 b that is adapted to be disposed within bone, and rod receiving portion 114 a, 114 b that is adapted to seat a spinal rod 104 a, 104b, or other spinal fixation element therein. The rod receiving portion 114 a, 114 b of each bone anchor 102 a, 102 b can include a proximal bearing surface 108 a, 108 b that has a shape or configuration that is adapted to match the shape or configuration of the connecting plate 106, as will be described in more detail below. The distal portion 110 a, 110 b of each bone anchor 102 a, 102 b can include a threaded shaft 192 a, 192 b and head 190 a, 190 b formed thereon and adapted to sit within and pivot related to the rod receiving portion 114 a, 114 b. As previously indicated, a person skilled in the art will appreciate that a variety of bone anchors known in the art can be used with the spinal fixation system 100.

The connecting plate 106 of the system 100 can also have a variety of configurations, but it is preferably adapted to span laterally across a vertebra such that the connecting plate 106 can extend between and couple to the bone anchors 102 a, 102 b implanted in opposed lateral sides of a vertebra. The connecting plate 106 is shown in more detail in FIGS. 2A-2C, and as shown the connecting plate 106 has a generally elongate shape with a spanning portion 124 having opposed ends 122 a, 112 b.

The spanning portion 124 can have a variety of configurations, including a planar configuration, or an arcuate shape as shown. In one exemplary embodiment, the spanning portion 124 can have a radius of curvature in a range of between about 5 mm and 15 mm, and more preferably about 8 mm and 12 mm. The spanning portion 124 of the connecting plate 106 can also vary with respect to thickness a, as indicated in FIG. 2C. In an exemplary embodiment, the thickness a is less that a width b of the plate, as indicated in FIG. 2B. Such a configuration allows for intraoperative contouring of the plate to accommodate patient anatomy yet also provides geometric stiffness to impart torsional rigidity to the plate and spinal construct. As is further shown in FIGS. 2A-2C, the spanning portion 124 can also be offset from a plane defined by the ends 122 a, 122 b of the connecting plate 106. For example, in one exemplary embodiment the spanning portion 124 can be offset by at least about 3 mm from a plane defined by the end 122 a, 112 b of the connecting plate 106, and more preferably the spanning portion 124 can be offset by between about 5 mm to 10 mm from a plane defined by the ends 122 a, 122 b of the connecting plate 106.

As is further shown, the connecting plate 106 can also include an opening 120 a, 120 b formed in each end 122 a, 122 b thereof for receiving a set screw 116 a, 116 b that mates to the rod-receiving portion 114 a, 114 b of each bone screw 102 a, 102 b. The openings 120 a, 120 b defined by the connecting plate 106 may circular, elliptical, polygonal, or have any other shape, as will be discussed in more detail below with respect to FIGS. 12A-14C. In operation, each end 122 a, 122 b is adapted to be positioned on top of the rod-receiving portion 114 a, 114 b of each bone screw 102 a, 102 b, as shown in FIG. 1B. The ends 122 a, 122 b and the rod-receiving portion 114 a, 114 b of each bone screw 102 a, 102 b can thus include bearing surfaces that are shaped to facilitate mating of the components, as will be discussed in more detail below.

As previously explained, the device 100 can also include a closure mechanism, such as a set screw 116 a, 116 b for mating the rods 104 a, 104 b to the bone anchors 102 a, 102 b. One of the sets screws, e.g., set screw 116 a, is shown in more detail in FIGS. 3A-3B. As shown, the set screw 116 a has a generally cylindrical shape with threads formed therearound for mating with corresponding threads formed within the rod-receiving portion 114 a of the bone anchor 102 a. In use, the set screw 116 a can be threaded into the bone anchor 102 a to lock the rod 104 a within the rod receiving portion 114 a of the anchor 102 a, as shown in FIG. 1B. A person skilled in the art will appreciate that a variety of techniques can be used to mate the set screw 116 a to the bone anchor 102 a including, for example, a twist-lock mechanism or other non-threaded closure mechanism.

The device 100 can also include one or more fastening elements for mating the connecting plate 106 to one or more bone anchors 102 a, 102 b. In an exemplary embodiment, the spinal fixation system 100 includes a locking nut or cap 118 a, 118 b that mates to each set screw 116 a, 116 b, which in turn are mated to the bone anchors 102 a, 102 b. Each cap 118 a, 118 b can have a variety of configurations. FIGS. 4A-4C illustrate cap 118 a in more detail. As shown, the cap 118 a has a generally circular shape with an opening formed therethrough and adapted to receive the set screw 116 a. The opening can include threads 152 a, or other mating features, formed therein and adapted to mate with corresponding threads, or other mating features, formed on the set screw 116 a. In use, as previously shown in FIG. 1B, the caps 118 a, 118 b are mated to the set screw 116 a after the opening 120 a, 120 b in the ends of the connecting plate 106 are positioned over the set screws 116 a, 116 b. An inferior bearing surface 140 a, 140 b of each cap 118 a, 118 b will thus engage the ends 122 a, 112 b of the connecting plate 106, locking the connecting plate 106 to the bone anchors 102 a, 102 b.

As previously indicated, the rod-receiving portion 114 a, 114 b of each bone screw 102 a, 102 b and the ends 122 a, 112 b of the connecting plate 106, as well as the caps 118 a, 118 b, can each have bearing surfaces that are shaped to facilitate mating of the components, and in particular to facilitate locking of the components in a fixed position relative to one another. For example, as shown in FIG. 2C, the connecting plate 106 can have an inferior bearing surface 138 b that is conical or spherical. A proximal surface 108 b of the bone anchor 102 b that mates with the connecting plate 106 can have a corresponding spherical or conical shape that bears against the inferior bearing surface 138 b on the connecting plate 106. In other embodiments, the bearing surface can have different shapes. For example, FIG. 5B illustrates a connecting plate 106′ having an inferior bearing surface 138 b′ that is conical while the bearing surface 108 b′ on the rod-receiving portion 114 b′ of the bone anchor is spherical.

Each cap 118 a, 118 b can also have a bearing surface that is shaped to match a corresponding bearing surface formed on a superior bearing surface 142 a, 142 b of the connecting plate 106. For example, FIGS. 4A and 4C illustrate cap 118 a having a distal bearing surface 140 that is concave to mate with a corresponding convex bearing surface formed on the superior bearing surface 142 a, 142 b of the connecting plate 106.

In other embodiments, the bearing surfaces may be spherical, convex, concave, flat, variations or combinations thereof, or they may have any other shape sufficient to facilitate coupling of the plate to the bone anchor.

The radius of curvature of the bearing surfaces can also vary. As shown in FIG. 5A, the spherical superior surface 108 b of the rod receiving portion 114 b can have a radius of curvature R1 that extends from the point about which the bone screw portion pivots. The bearing surface 140 b of cap 118 b can have a radius of curvature R4 that extends from the point about which the bone screw portion pivots. The inferior and superior bearing surfaces 138 b, 142 b of the connecting plate 106 can also have radii of curvature R2 and R3 that extends from the point about which the bone screw portion pivots. In other embodiments, the radii may extend from a point distinct from the pivot point of the bone screw. In certain exemplary embodiments, each of the radii R1, R2, R3 and R4 can be in a range between about 5 mm and 15 mm.

FIGS. 6A and 6B illustrate another embodiment of a spinal fixation system. In this embodiment, each bone anchor 102 a, 102 b includes a compression member 196 a, 196 b disposed within the rod-receiving portion 114 a, 114 b and that defines a rod seat 198 a, 198 b adjacent to the head 190 a, 190 b of the bone screw portion 110 a, 110 b. During operation of the spinal fixation system 100, the compression member 196 a, 196 b is disposed between the rod 104 a, 104 b and the head 190 a, 190 b of each bone anchor portion 110 a, 110 b.

As is further shown in FIGS. 6A and 6B, the cap 119 a, 119 b used to lock the connecting plate 106″ has a threaded post that extends into and mates with corresponding threads formed in the set screw 154 a, 154 b mated to each bone anchor 102 a, 102 b. Set screw 154 a is shown in more detail in FIGS. 7A-7D, and as shown the set screw 154 a has a threaded bore 156 a for mating with cap 119 b. The set screw 154 a also has a length that is less than a length of the set screws 116 a, 116 b illustrated in FIGS. 1A and 1B. An alternative embodiment of a set screw 154′ having a threaded bore 156′ for mating with cap 119 a, 119 b is shown in FIGS. 8A-8D.

FIGS. 6A and 6B also illustrate various embodiments of bearing surfaces on the various components. For example, in FIG. 6A the inferior bearing surface 139 b on the cap 119 b is flat and it is received with a conical or concave bearing surface 142 b″ formed in the connecting plate 106″. FIG. 6B also illustrates a cap 119 a having a flat bearing surface 139 a, however the cap 119 a rests against the superior surface of the connecting plate 106″. Another embodiment of a cap 119′ with a threaded shaft is shown in FIG. 9, and in this embodiment the bearing surface 139′ is concave.

FIG. 10 illustrates another embodiment of a spinal fixation system 100′. In this embodiment, spinal fixation 100′ includes a floating washer 144 to allow the connecting plate 150 to be used with bone anchors 110 a, 110 b positioned at various distances from one another. As shown in more detail in FIGS. 11A-11C, the floating washer 144 includes a bearing surface 146 that mates with a distal bearing surface 140 of cap 118, and rails 148 that slidably engage the connecting plate 150. In use, the floating washer 144 can be slide onto the connecting plate 150, which as shown in FIG. 10 has an elongate slot formed thereon. The floating washer 144 can be positioned as desired relative to the elongated slot, and then mated to the bone anchor 102 b using cap 118 b and set screw 116 b. The connecting plate 150 is thereby fixed to the bone anchor 102 b by compression between the floating washer 144 and the bone anchor 102 b.

As previously indicated, the connecting plate can have a variety of other configurations. For example, as indicated above, the connecting plate 150 shown in FIG. 10 has one end with an elongate slot formed therein for allowing the bone anchor 102 b to be mated to the connecting plate 150 at a selected position. FIGS. 12A-14C illustrate various other exemplary embodiments of a connecting plate. In the embodiment shown in FIGS. 12A-12C, the connecting plate 160 includes a spanning portion 164 extending between opposed ends, each end having an elongated opening 166, 166′ formed therein. The ends can also includes rails 162 configured to mate with a washer 144. FIGS. 13A-13C illustrate another embodiment of a connecting plate 170. In this embodiment, the spanning portion 174 extends between a first end 172 having an elongate slot 176 formed therein and having side rails configured to mate with a washer 144, and a second end 172′ having a circular opening 176′ formed therein. In yet another embodiment, as shown in FIGS. 14A-14C, the connecting plate 180 can include a spanning portion 184 extending between a first end 182 with a circular opening 186, and a second end 182′ with an open-ended opening 186′.

In other embodiments, the connecting member can be in the form of a rod rather than a plate. A band clamp or other fastening element can be used to mate the rod to the bone anchors. FIGS. 15A-B illustrate a spinal fixation system 500 having first and second bone anchors 502 a, 502 b, first and second band clamps 504 a, 504 b, a connecting rod 506, and first and second dovetail threaded post subassemblies 508 a, 508 b. The threaded post subassemblies 508 a, 508 b mate to the bone anchors 502 a, 502 b, respectively, and the band clamps 504 a, 504 b mate the connecting rod 506 to the subassemblies 508 a, 508 b, respectively. Other features and methods of operation of system 500 are substantially similar to those disclosed herein for system 100.

During operation, referring back to the embodiment shown in FIGS. 1A and 1B, for example, the first and second bone anchors 102 a, 102 b can be implanted in opposed lateral sides of a vertebra. One or more additional bone anchors can be implanted in one or more adjacent vertebra. A spinal fixation element, such as spinal rods 104 a, 104 b can be positioned within the rod-receiving portion 114 a, 114 b of each bone anchor 102 a, 102 b, and optionally within the rod-receiving portion of one or more bone anchors implanted in one or more adjacent vertebrae. The sets screws 116 a, 116 b are then mated to the bone anchors 102 a, 102 b to lock the rod therein. The connecting plate 106 can then be positioned to span between the bone anchors 102 a, 102 b. In particular, the first end 122 a of the connecting plate 106 can be positioned over the first set screw 116 a, and the second end 122 b of the connecting plate 106 can be positioned over the second set screw 116 b. Caps 118 a, 118 b can then be threaded onto the set screws 116 a, 116 b to lock the connecting plate 106 to the bone anchors 102 a, 102 b, thereby stabilizing the bone anchors 102 a, 102 b.

In another embodiment the connecting plate can be adapted to span between a bone anchor and a posterior element of a vertebra. For example, FIGS. 16A-16C illustrate a connecting plate 130 having a spanning portion 136 with a buttress 132 formed on an inferior surface 134. In use, as shown in FIG. 17A, the connecting plate 160 can be used to decompress the spinal canal. As shown, a first dissection 204 is made in a posterior element 200 of a vertebra, and the posterior element 200 is then moved to expand the spinal canal 202. The connecting plate 130 is then coupled to a bone anchor 102 b implanted in the vertebra and to the posterior element 200 to maintain the posterior element 200 in a fixed position. In one embodiment, the posterior element 200 can be a portion of the lamina of the vertebra. In another embodiment, the posterior element 200 can be the spinous process of the vertebra.

The method can also include making a second dissection 206 on the contralateral side of the posterior element 200 opposite to the first cut 204, as shown in FIG. 17B. The posterior element 200 is then moved to expand the second cut 206, and a second connecting plate 130′ is then coupled to a second bone anchor 102′ and the posterior element 200′ to maintain the second cut 206 in the expanded position. As a result, the spinal canal is enlarged. In an exemplary embodiment, the bone anchors 102 a, 102 b are implanted in the lateral mass 208 of the vertebra, for example in the pedicles.

While the previous embodiments relate to cross connectors for mating two bone anchors, or for mating a bone anchor to a posterior element, in another embodiment a cross-connector is provided for mating a bone anchor to a spinal fixation element, such as a rod, cable, tether, etc. Some injuries allow only a single bone anchor to be implanted on a lateral side of a vertebra, preventing a second bone anchoring from being implanted on an opposed lateral side of the vertebra. However, it may be desirable to provide additional support to the bone anchor that is implanted in the vertebra. Accordingly, a head-to-rod cross connector is provided for coupling a bone anchor implanted on a first lateral side of a vertebra to a spinal fixation element, such as a spinal rod, spanning across an opposed lateral side of the vertebra.

FIGS. 18A-18C illustrate one exemplary embodiment of a spinal stabilization system 10 having a head-to-rod cross connector 12. The spinal stabilization system 10 is similar to the previously described systems, except that one end of the cross connector can mate directly to a spinal fixation element, such as a spinal rod, without anchoring to bone. In particular, the second end 12 b of the cross connector 12 includes a coupling member 20 for mating the second end 12 b of the cross connector 12 directly to a spinal fixation element, such as spinal rod 40 b as shown. The first end 12 a of the cross connector 12, as well as the bone screw 30, spinal rod 40 a, and fastening element, which includes set screw 14 a and locking cap 16 a, are similar to previously described embodiments, and thus they will not be discussed in detail with respect to FIGS. 18A-18B. The cross connector 12 can also include floating washers 18 a, 18 b, as shown, to facilitate mating of the cross connector 12 to the first and second spinal rods 40 a, 40 b at a particular location. Exemplary floating washers were previously described with respect to FIGS. 10-11C.

The coupling member 20 can have a variety of configurations, and it can be adapted to mate to a spinal rod 40 a and to the second end 12 b of the cross connector 12 using a variety of techniques. In the illustrated embodiment, as shown in FIG. 18A-18C, the coupling member 20 is in the form of a housing having a rod-receiving recess 20 a formed therein for seating a spinal fixation element, such as spinal rod 40 b. The illustrated rod-receiving recess 20 a has a substantially concave shape to seat a cylindrical rod 40 b extending therethrough, and it is defined by a top wall 20 t, a bottom wall 20 b, and a sidewall 20 s connecting the top and bottom walls 20t, 20 b. As a result, the coupling member 20 is a side-loading coupling member 20, i.e., it loads onto a spinal rod 40 b from the side.

The coupling member 20 can mate to the second end 12 of the cross connector 12 using a variety of mating techniques. In the illustrated exemplary embodiment, the coupling member 20 includes an opening 20 c formed in the top wall 20 t thereof for receiving a fastening element, such as set screw 12 b. The opening 20 c can extend into the rod-receiving recess 20 a to allow the set screw 12 b to abut against a spinal rod 40 b disposed therein, thereby locking the rod 40 b to the coupling member 20, and thus to the cross connector 12. The fastening element can also including a locking cap 16 b, similar to those previously described, that mates to the set screw 14 b and that bears against the cross connector 12 to lock the cross connector 12 to the coupling member 20. A person skilled in the art will appreciate that the fastening element can have a variety of other configurations, including those described herein as well as those known in the art. The cross connector 12 can also have a variety of other configurations, and it can include other features to facilitate mating to the coupling member 20.

In use, as shown in FIG. 18A, the first end 12 a of the coupling member 20 can be mated to a bone anchor 30 that is implanted in a lateral side of a first vertebra. In particular, a set screw 14 a can be inserted through a thru-bore or opening 13 a formed in the first end 12 a of the cross connector 12, and it can be threaded into the rod-receiving portion 32 of the bone screw 30 to lock a spinal rod 40 a in the rod-receiving recess 32 a. A locking cap 16 a can be threaded onto an opposed end of the set screw 14 a to lock the cross connector 12 to the bone anchor 30. The second end 12 b of the cross connector 12 can be mated to a spinal rod 40 b that extends substantially parallel to spinal rod 40 a on an opposed lateral side of the first vertebra, and that is not anchored to the first vertebra. In particular, the coupling member 20 can be side loaded onto the spinal rod 40 b, and a set screw 14 b can be inserted through an opening or thru-bore 13 b formed in the first end of the cross connector 12 and into the opening 20 c formed in the coupling member 20 to lock the rod 40 b within the rod receiving recess 20 a of the coupling member 20. The cross connector 12 can alternatively be placed over the set screw 14 b after the set screw 14 b is mated to the coupling member 20. The locking cap 16 b can be threaded onto an opposed end of the set screw 14 b to lock the cross connector 12 to the coupling member 20. The coupling member thus provides additional support to a spinal stabilization system implanted in a patient's spine without requiring both ends of the cross connector to anchor to bone. A person skilled in the art will appreciate that both end of the cross connector can mate to first and second spinal fixation elements, such as spinal rods, without anchoring to bone. For example, first and second coupling member can be used to mate a cross connector to first and second spinal rods extending along opposed lateral sides of a vertebra.

As indicated above, the coupling member can have a variety of other configurations, and various techniques can be used to mate the coupling member to a spinal fixation element, such as a spinal rod, and to the cross connector. FIGS. 19A-19C illustrate another embodiment of coupling member 320. The coupling member 320 is illustrated as part of a spinal stabilization system 300 which, like previous embodiments, generally includes a cross connector 312 having a first end 312 a that is adapted to mate to a bone anchor 330, and a second end 312 b that is adapted to mate to a coupling member 320. A first fastening element, which includes a set screw 314 a and a locking cap 316 a, is provided for locking the first end 312 a of the cross connector 312 to the bone screw 330, and for locking a spinal rod 140 a in the rod-receiving portion of the bone screw 330, and a second fastening element, which includes a set screw 314 b and a locking cap 316 b, is provided for locking the second end 312 b of the cross connector 312 to the coupling member 320. In the embodiment shown in FIGS. 18 a-18C, the set screw 14 a was effective to directly contact the spinal rod 40 a to lock the spinal rod 40 a in the rod-receiving recess 20 a of the coupling member 20. In this embodiment, the set screw 314 a does not directly engage the spinal rod 340 a, but rather the coupling member 320 includes a locking arm 322 disposed therein for engaging the spinal rod 340 a. The coupling member 320 is also top loading, rather than side loading.

The locking arm 322, which is best shown in FIG. 19A, can have a variety of shapes and sizes, but in an exemplary embodiment it is adapted to extend around at least a portion of a spinal rod 340 a disposed within the rod-receiving recess 320 a, and it is adapted to engage the rod 340 a when the set screw 314 b is mated to the coupling member 320 a. In particular, the locking arm 322 can have an elongate configuration with a first end 322 a that is adapted to be pivotally disposed within an elongate opening 321 formed in a sidewall 320 s of the coupling member 320, and a second or terminal end 322 b that is curved and that extends into the rod-receiving recess 320 a of the coupling member 320 a. The locking arm 322 can also extend across the path of the opening formed in the top wall 320 t of the coupling member 320 that receives the set screw 314 b. As a result, when the set screw 314 b is inserted through the opening in the top wall 320 t of the coupling member 320 it will bear down on the locking arm 322, thereby causing the curved terminal end of the locking arm 322 to pivot downward and engage the spinal rod 340 b.

In use, the coupling member 320 a is inserted over the spinal rod 340 b, i.e., the spinal rod 340 b is bottom loaded into the rod-receiving recess 320 a of the coupling member 320. The set screw 314 b is then inserted through the opening formed in the second end 312 b of the cross connector 312 and into the opening formed in the coupling member 320 a to bear against the locking arm 322, thereby causing the locking arm 322 to engage and lock the spinal rod 340 a within the rod-receiving recess 320 a of the coupling member 320. The cross connector 312 can alternatively be placed over the set screw 314 b after the set screw 314 b is mated to the coupling member 320. The locking cap 316 b can then be threaded onto the set screw 314 b to lock the cross connector 312 to the coupling member 320.

FIG. 20 illustrates yet another embodiment of a coupling member 420. In this embodiment, the coupling member 420 includes two rod-engaging members or wedges 422 a, 422 b slidably disposed within the coupling member 420. The wedges 422 a, 422 b can have a variety of configurations and they can be mated to or disposed within the coupling member 420 using a variety of techniques, but they are preferably effective to move linearly in response to a force applied thereto by a set screw 414 to lock a spinal fixation rod 420 within the rod-receiving recess 420 a of the coupling member 420. In an exemplary embodiment, the coupling member 42 includes first and second receiving cavities (not shown) formed therein for slidably seating the wedges 422 a, 422 b. The first and second cavities preferably extend between the opening 420 o formed in the top wall 420 s of the coupling member 420 that receives the set screw 414, and the rod-receiving recess 420 a. The cavities are also preferably spaced a distance apart from a bottom surface 420 b of the coupling member 420 to allow the wedges 422 a, 422 b to be retained within the coupling member 420.

In use, the coupling member 420 can be top loaded onto a spinal rod 420 a, and the set screw 414 can be inserted, e.g., threaded, into the opening 420 o in the coupling member 420. The set screw 414 will thus bear against the opposed wedges 422 a, 422 b, thereby driving the wedges 422 a, 422 b linearly such that the extend into the rod-receiving recess 420 a. As a result, the wedges 422 a, 422 b will engage the spinal rod 440, thereby locking the rod 420 a to the coupling member 420. As previously described, a cross connector can be mated to the coupling member 420 using a locking cap of other locking mechanism.

FIGS. 21A-21B illustrate yet another embodiment of a coupling member 520 that can be used to couple a cross connector to a spinal rod without anchoring the cross connector to bone. In this embodiment, the coupling member 520 includes a single wedge or shoe 522 disposed therein. The shoe 522 is disposed within a cavity 521 that is laterally offset from the rod receiving recess 520 a formed in the coupling member 520. In particular, the cavity 512 extends from a top wall 520 t toward a bottom wall 520 b. The cavity 512 can terminate prior to the bottom wall 520 b such that the bottom wall 520 is effective to retain the shoe 522 therein. The shoe 522 is adapted to sit within the cavity 521 and is movable from a distal position to a proximal position, i.e., the shoe 522 moves from a resting position adjacent to the bottom wall 520 b toward the top wall 520 a. Movement of the shoe 522 can be achieved using a set screw 514 that is inserted through an opening 520 o formed in the top surface 520 t of the coupling member 520, and through an opening 522 a formed in the shoe 522. As the set screw 514 is threaded or otherwise mated to the shoe 522, the set screw 514 can pull the shoe 522 toward the top wall 520 t. In an exemplary embodiment, the set screw 514 can include a proximal portion 514 a that is adapted to mate with and engage the coupling member 520, and a distal portion 514 b that is adapted to mate with and engage the shoe 522. The proximal and distal portions 514 a, 514 b can have a different size, e.g., diameter, thread pitch, etc. Such a configuration allows the set screw 514 to move the shoe 522 proximally while maintaining the coupling member 520 in a substantially fixed position. As a result of the movement of the shoe 522, a wedge-shaped protrusion 522 b extending into the rod-receiving recess 502 a of the coupling member 520 will move toward the top wall 520 t, thereby engaging a spinal rod 540 disposed within the rod-receiving recess 520 a, as shown in FIG. 21B. A locking cap 516 can then be applied to the proximal portion 514 a of the set screw 514 to mate a cross connector to the coupling member 520.

One of ordinary skill in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety. 

What is claimed is:
 1. A spinal fixation system, comprising: a bone anchor having a bone-engaging portion and a rod receiving portion with opposed arms configured to receive a rod therebetween; a connecting member having first and second ends, the first end having an opening extending therethrough and having a distal surface that bears against a proximal terminal end surface of each of the opposed arms of the rod receiving portion of the bone anchor; and a closure mechanism having a portion that extends through the opening in the first end of the connecting member and having threads formed thereon and configured to threadably engage threads formed on the opposed arms of the rod receiving portion of the bone anchor.
 2. The spinal fixation system of claim 1, wherein the closure mechanism comprises a set screw.
 3. The spinal fixation system of claim 1, further comprising a fastening element configured to mate to the closure mechanism to lock the connecting member to the rod receiving portion of the bone anchor.
 4. The spinal fixation system of claim 3, wherein the fastening element comprises a locking nut configured to threadably engage the closure mechanism.
 5. The spinal fixation system of claim 3, wherein the fastening element includes a head and a threaded shank that extends distally from the head.
 6. The spinal fixation system of claim 5, wherein a distal-facing surface of the head of the fastening element is configured to bear against a proximal surface of the first end of the connecting member, and wherein the threaded shank extends from the distal-facing surface and is configured to extend into a threaded bore formed in the closure mechanism.
 7. The spinal fixation system of claim 1, wherein, when a rod is disposed between the opposed arms of the rod receiving portion, the connecting member is oriented at an angle in a range between about 20° and about 160° relative to the rod.
 8. The spinal fixation system of claim 1, wherein, when a rod is disposed between the opposed arms of the rod receiving portion, the connecting member is oriented at an angle in a range between about 60° and about 120° relative to the rod.
 9. The spinal fixation system of claim 1, wherein the bone anchor comprises a polyaxial screw.
 10. A spinal fixation system, comprising: a bone anchor having a bone-engaging portion and a rod receiving portion with opposed arms that receive a rod therebetween; a rod disposable between the opposed arms of the rod receiving portion of the bone anchor; a connecting member having first and second ends, the first end having a distal surface that bears against a proximal terminal end surface of the opposed arms of the rod receiving portion of the bone anchor; and a set screw configured to extend through an opening formed in the first end of the connecting member and having threads configured to threadably engage the opposed arms of the rod receiving portion of the bone anchor.
 11. The spinal fixation system of claim 10, further comprising a fastening nut configured to threadably mate to the set screw to lock the connecting member to the rod receiving portion of the bone anchor.
 12. The spinal fixation system of claim 10, further comprising a fastening element having a head and a threaded shank that extends distally from the head and that is configured to extend into a threaded bore formed in the set screw.
 13. The spinal fixation system of claim 12, wherein a distal-facing surface of the head of the fastening element is configured to bear against a proximal surface of the first end of the connecting member.
 14. A spinal fixation system, comprising: first and second bone anchors, each bone anchor having a bone-engaging portion and a rod receiving portion with opposed arms that receive a rod therebetween; a fixation element disposable between the opposed arms of the rod receiving portion of the first and second bone anchors for connecting the first and second bone anchors; a cross connector configured to span between opposed lateral sides of a vertebra and having first and second ends, the first end of the cross connector having a distal surface that bears against a proximal terminal end surface of the opposed arms of the rod receiving portion of the first bone anchor; a closure mechanism configured to mate to the opposed arms of the rod receiving portion of the first bone anchor to lock the fixation element to the first bone anchor; and locking element configured to engage the closure mechanism to lock the cross connector to the rod receiving portion of the first bone anchor.
 15. The spinal fixation system of claim 14, wherein a portion of the closure mechanism is configured to extend through the first end of the cross connector when the closure mechanism is mated to the opposed arms.
 16. The spinal fixation system of claim 14, wherein the closure mechanism comprises a set screw that threadably mates with threads formed on the opposed arms of the rod receiving portion of the first bone anchor.
 17. The spinal fixation system of claim 14, wherein the locking element comprises a locking nut configured to threadably mate to the closure mechanism.
 18. The spinal fixation system of claim 14, wherein the locking element includes a head and a threaded shank, the threaded shank being configured to threadably mate with a threaded bore formed in the closure mechanism. 